1. Field of the Invention
The present invention relates to a master making device for making a master and a stencil printer including the same.
2. Discussion of the Background
A digital stencil printer is simple in construction and easy to operate and uses a thermosensitive stencil having a laminate structure. The stencil is made up of a thermosensitive resin film usually 1 .mu.m to 2 .mu.m thick and a porous substrate adhered to the film. The porous substrate is implemented by Japanese paper fibers or synthetic fibers of a mixture thereof. While the film surface of the stencil is held in contact with heating elements arranged on a thermal head, the head is operated in the main scanning direction in order to selectively perforate the stencil with the heating elements in accordance with an image signal. A platen roller or similar conveying means conveys the stencil in the subscanning direction for thereby completing a master. The master is automatically wrapped around a rotatable drum made up of a porous hollow cylinder and a plurality of mesh screens covering the cylinder. The mesh screens are formed of resin or metal. Ink is fed from ink feeding means disposed in the drum. A sheet is fed by a press roller, a press drum having substantially the same diameter as the drum or similar pressing means. The sheet is continuously pressed against the drum via the master. As a result, the ink is transferred from the drum to the sheet via a porous portion included in the drum and the perforations of the master.
Usually, the stencil for the above application is paid out from a roll mounted on a tubular paper core. The roll is rotatably set on a holder member playing the role of master storing means included in a master making device. The operator of the printer pulls the leading edge of the stencil away from the roll and inserts it between the thermal head and the platen roller or between a pair of conveyor rollers. Thereafter, the stencil is conveyed to the downstream side in a direction of stencil transport. After the leading edge of the stencil has been cut off for a matching purpose, a sequence of steps for wrapping a master around the drum are executed.
The resin film included in the stencil is apt to be charged by static electricity. The stencil is therefore apt to adhere to the platen roller or the conveyor rollers when inserted between the thermal head and the platen roller or between the conveyor rollers, jamming a stencil transport path. Further, the ink is transferred from the drum to the sheet via the Japanese paper fibers, or porous substrate, and the perforations of the resin film. This brings about a problem that when the fibers of the substrate are entangled in masses or when thick fibers extend across the perforations of the resin film, a solid image is locally lost or fine lines or characters are disconnected or blurred due to so-called fiber marks.
In light of the above, there has been proposed to omit the porous substrate which is the cause of fiber marks, to reduce the thickness of the porous substrate, or to implement the stencil substantially only with a thermoplastic resin film. However, a stencil with any of such configurations is lower in elasticity than the conventional stencil and therefore apt to jam, e.g., a master making and feeding section. It is to be noted that the stencil implemented substantially only with a thermoplastic resin film also refers to a stencil having a thermoplastic resin film containing a trace of anti-static agent or similar component, and a stencil having a thermoplastic resin film having at least one of opposite major surfaces covered with one or more overcoat layers or similar thin layers.
Japanese Utility Model Laid-Open Publication No. 63-178134, for example, discloses a stencil printer of the type including a document reading section for reading a document image arranged above a master making and feeding section disposed in the printer. This type of stencil printer is capable of reading a document image and making a master at the same time consistently within itself. However, a problem with this type of stencil printer is that a portion for mounting the document reading section must have its mechanical strength, weight and number of parts increased in order to allow the stencil to be set or replaced and allow a jam to be dealt with. This increases the machining cost and cost of assembly of the constituent parts and therefore the overall cost of the printer. Moreover, only a limited space is available for the operator to set or replace the stencil or to deal with a jam, resulting in troublesome work.
To replace or set the stencil in the master making and feeding section or to deal with a master jam or similar jam, it has been customary for the operator to slide the document reading section sideways or open it upwardly so as to provide access from above the reading section. However, sliding or opening the document reading section is not only troublesome to perform, but also causative of the dislocation of the document from its initial position. Specifically, in a document reading section of the type reading a document by moving its scanner relative to the document, vibration ascribable to the reading section slid in a preselected direction in the event of a jam causes the document to move on a glass platen. It is therefore necessary for the operator to open a document table again and set the document on the glass platen correctly. This is also true with a document reading section using an ADF (Automatic Document Feeder) or an RDF (Recycling Document Feeder) or RDH (Recycling Document Handler) for setting a document on a glass platen.
On the other hand, in a document reading section of the type moving a document relative to a stationary scanner, the document is continuously conveyed by, e.g., an ADF to a discharge tray by way of a glass platen and is therefore free from dislocation. However, when a master jams the master making and feeding section, it should be picked out of the master making and feeding section via the top of the section without exception, also resulting in troublesome work. In a conventional stencil printer with such a document reading section, assuming that a trouble occurs in the document reading section, sheet discharging section or sheet feeding section different from the master making and feeding section, and that a jam occurs in the master making and feeding section at the same time. Then, the jam must also be dealt with from above the master making and feeding section, also resulting in troublesome work.
The problems discussed above are particularly true with a stencil printer including a master making and feeding section provided with master stocking means which stocks a perforated part of a stencil or master for a moment.